1. Field of the Invention
The present invention relates to a deflection yoke, and more particularly to a deflection yoke having a non-magnetic conductor added to a vertical coil (hereinafter simply referred to as "V coil") in order to improve a ringing phenomenon caused by stray capacitance between a horizontal deflection coil (hereinafter simply referred to as "H coil") and V coil and stray capacitance between the V coil and a ferrite core.
2. Description of the Prior Art
Generally, deflection yokes mounted on the rear portion of cathode ray tubes in televisions and monitors are classified into a saddle-saddle type deflection yoke, a saddle-toroidal type deflection yoke, and a bobbin type deflection yoke. Respective deflection yokes include V coils for deflecting electron beams in the vertical direction of a screen, H coils for deflecting the electron beams in the horizontal direction of the screen, a coil separator for determining the structure of the deflection yoke, and magnetic members, i.e., ferrite cores, for increasing the deflection force.
The general structure of the deflection yoke will be described with reference to FIG. 1. As illustrated in FIG. 1, a deflection yoke 1 is provided with a pair of front screen-bent and rear neck-bent saddle-shaped H coils 3 on the inner side of a coil separator 2 in the up and down direction, using a horizontal axis of the deflection yoke 1 as a reference. Using the horizontal axis of the deflection yoke as a reference, a pair of front screen-bent and rear neck-bent saddle-shaped V coils 4 are mounted on the outer side of the coil separator 2 in the left to right direction. A pair of ferrite cores 5 are installed to surround the V coils 4. The ferrite cores 5 are fixed by a core clamp (not shown). The deflection yoke 1 having the above-described construction is installed on tile rear portion of a cathode ray tube.
At this time, when the deflection yoke is supplied with a pulse voltage as shown in FIG. 2A, sawtooth current (as shown in FIG. 2B) is supplied to the H coil 3 and V coil 4 of the deflection yoke 1, respectively, so that respective deflection magnetic fields are generated by the H coil 3 and the V coil 4. That is, as shown in FIG. 2C, RGB electron beams scanning while passing through the center portion of the deflection yoke 1 are deflected in horizontal and vertical directions prior to forming a picture by scanning, due to the horizontal and vertical deflection magnetic fields respectively generated by the H coil 3 and V coil 4. Meantime, in the deflection yoke constructed as above, the spacing between the H coil 3 and V coil 4 and that between the V coil 4 and ferrite core 5 are so narrow to cause a magnetic force and an electric force of a predetermined magnitude between the H coil 3 and V coil 4 or the V coil 4 and ferrite core 5.
Here, the generation of the magnetic force is the same as the publicly-known theory of a transformer. In more detail, as illustrated in FIG. 4, once the H coil 3 is supplied with a voltage V1 to flow current, a magnetic field is induced from the B coil 3 to the V coil 4 as much as a predetermined value in accordance with the coiled ratio of the H coil 3 and V coil 4, which can be written as: ##EQU1## where V denotes a voltage and L is an inductance of the coil.
Also, as shown in FIG. 4, since stray capacitance occurs between the H coil 3 and V coil 4, and V coil 4 and ferrite core 5, the electric force is generated. The reason of the occurrence of the stray capacitance is in that the horizontal deflection voltage V1 is much greater than a vertical deflection voltage V2 to cause two voltage differences. In other words, while the horizontal deflection voltage V1 has a range of -20 to 1000 [V], the vertical deflection voltage V2 has a range of 0 to 20 [V]. Therefore, the voltage difference between the two voltages is so great that a predetermined amount of electric charge exists between the two coils 3 and 4 which is the same as the theory of a capacitor, which can be defined as below: EQU Q=C.times.V (equation 2)
where Q denotes an amount of the electric charge, C is the capacitance, and V is the voltage.
Also, in the H coil 3 and V coil 4, since respective coils 3 and 4 are adjacently installed to induce the stray capacitance having the electric force with respect to coils 3 and 4. The stray capacitance inconsistently distributed throughout the H coil 3 or V coil 4 affect the sawtooth current supplied to the H coil 3 and the V coil 4.
When the magnetic force and electric force affect the sawtooth current supplied to the H coil 3 and V coil 4, an irregular waveform A as shown in FIG. 5B is generated to make the electron beams irregularly scan the left portion of the screen as shown in FIG. 5C, thereby causing black and white stripes. This is called as a ringing phenomenon.
A conventional technique for improving the ringing phenomenon will be described with reference to Japanese Patent Laid-open Publication No. sho 58-34549.
As illustrated in FIG. 6, a center tap 6 is drawn out of the center of the V coil 4, and damping resistors 7 and 8 of several k, respectively, are connected between the center tap 6, and a start terminal VS and a final terminal VF.
The deflection yoke constructed as above can damp a resonance phenomenon caused owing to the inherent inductance of the V coil 4 and the stray capacitance existing at the V coil 4, which results in decreasing resonance current in accordance with a pulse voltage, thereby improving the ringing.
However, when coiling the V coil 4 of the deflection yoke 1, a half of the V coil 4 is coiled by running a typical coiling machine, and an operator stops the coiling machine to draw out the end of the coiled V coil 4 and fix the drawn out coil to a link. Thereafter, the coiling machine is operated again to coil remaining half of the V coil 4.
In this case, the process for drawing out the center tap of the V coil is very fastidious, and lengthens working hours.
Moreover, if a coiling machine capable of drawing out the center tap is intended to be employed, the coiling machine should be additionally purchased to require additional cost.
On the other hand, referring to Japanese Patent Laid-open Publication No. sho 61-104544 as shown in FIG. 7, a thin conductive members 9 are respectively adhered on the surfaces of the upper coil and lower coil of the H coil 3, i.e., from the start terminal to the center of the coil.
That is, the conductive members 9 are adhered to the left and right of the upper coil and the left and right of the lower coil one by one, so that one deflection yoke has four conductive members 9.
In the deflection yoke having the above-described structure, since the stray capacitance inconsistently distributed throughout the H coil 3 can be mutually exchanged by means of the conductive members 9, the stray capacitance throughout the H coil 3 can be regularly distributed to improve the ringing.
However, in the above technique, once a voltage is supplied to the H coil attached with the conductive member, the horizontal deflection magnetic field generated by the supplied voltage is induced by the conductive member, and current flows in the direction vertical to the direction of the magnetic field due to the horizontal deflection magnetic field to reduce horizontal deflection current. Thus, a horizontal deflection amplitude is decreased. Furthermore, the current generated by the conductive member heats the conductive member, and the characteristic of the deflection yoke is changed due to the heat.